Bottom Pour Ladle and Method of Transferring Liquid Metal with Same

ABSTRACT

A bottom pour ladle device for transferring liquidus metal alloy from a crucible to a shot sleeve includes a bowl, snout, aperture, stopper, actuator, and stopper rod. The snout is disposed below the bowl and is configured to fit into the shot sleeve. A distal end of the snout is configured to reach a bottom portion of the shot sleeve. The aperture is at the distal end of the snout. The stopper is to close the aperture in response to being urged against the aperture. The actuator is to urge the stopper. The stopper rod is to connect the stopper to the actuator. The bowl, snout, and aperture are comprised of materials compatible with liquidus metal alloy.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser. No. 61/017,073, filed on Dec. 27, 2007, titled “BOTTOM POUR LADLE AND METHOD OF TRANSFERRING LIQUID METAL WITH SAME,” the disclosure of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a bottom pour ladle device. More particularly, the present invention relates to a bottom pour ladle device and method for transferring liquid metal with same.

BACKGROUND OF THE INVENTION

In the casting industry, a supply of liquid metal is maintained at liquidus temperatures in a crucible or reservoir. Depending upon the particular method of casting, this liquidus metal is transferred from the crucible to a mold for casting an item. Certain automobile components are typically made via cast methods such as high pressure die casting (“HPDC”) or squeeze casting. In such high pressure devices, the liquidus metal is generally transferred to a hydraulic press or shot sleeve that injects the liquidus metal into the mold at high pressures.

Conventionally, a ladle may be used to dip into the crucible and retrieve a measure of liquidus metal that is then poured into the shot sleeve. Unfortunately, conventional ladles include elements that are not compatible with some alloys. In addition, these convention ladles are not capable of transferring liquidus metals without causing a great deal of turbulence. In some relatively reactive alloys, this turbulence may cause the formation of oxides or other such impurities that in turn adversely affect the quality of the casting.

SUMMARY OF THE INVENTION

The foregoing needs are met, to a great extent, by the present invention, wherein in some embodiments a bottom pour ladle and method for transferring liquidus magnesium alloy are provided.

An embodiment of the present invention relates to a bottom pour ladle device for transferring liquidus metal from a crucible to a shot sleeve. The device includes a bowl, snout, aperture, stopper, actuator, and stopper rod. The snout is disposed below the bowl and is configured to fit into the shot sleeve. A distal end of the snout is configured to reach a bottom portion of the shot sleeve. The aperture is at the distal end of the snout. The stopper is to close the aperture in response to being urged against the aperture. The actuator is to urge the stopper. The stopper rod is to connect the stopper to the actuator. The bowl, snout, and aperture are comprised of materials compatible with liquidus alloy.

Another embodiment of the present invention pertains to an apparatus for transferring liquidus alloy from a crucible to a shot sleeve. The apparatus includes a means for disposing a bottom pour ladle in the crucible. The bottom pour ladle has a bowl and a snout disposed below the bowl. The snout has an aperture at a distal end. The apparatus includes a means for opening the aperture to allow an ingress of liquidus alloy, means for closing the aperture to retain the liquidus alloy, and means for disposing the distal end at a bottom portion of the shot sleeve. In addition, the apparatus includes a means for opening the aperture to allow the liquidus alloy to flow into the shot sleeve and means for raising the bottom pour ladle, wherein the aperture is raised at a rate coinciding with a rate the shot sleeve fills with liquidus alloy and the aperture is controlled to remain relatively below a fill level of the shot sleeve.

Yet another embodiment of the present invention relates to a method of transferring liquidus alloy from a crucible to a shot sleeve. In this method, a bottom pour ladle is disposed in the crucible. The bottom pour ladle has a bowl and a snout disposed below the bowl. The snout has an aperture at a distal end. In addition, the aperture is opened to allow an ingress of liquidus alloy, the aperture is closed to retain the liquidus alloy, and the distal end is disposed at a bottom portion of the shot sleeve. Furthermore, the aperture is opened to allow the liquidus alloy to flow into the shot sleeve and the bottom pour ladle is raised. The aperture is raised at a rate coinciding with a rate the shot sleeve fills with liquidus alloy and the aperture is controlled to remain relatively below a fill level of the shot sleeve.

There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified view of a horizontal vertical squeeze casting apparatus according to an embodiment of the invention.

FIG. 2 is a simplified view of the horizontal vertical squeeze casting apparatus during a shot sleeve filling operation.

FIG. 3 is a cross sectional view of a bottom pour ladle during an initial stage of the shot sleeve filling operation.

FIG. 4 is a cross sectional view of a bottom pour ladle during an intermediate stage of the shot sleeve filling operation.

FIG. 5 is a cross sectional view of a bottom pour ladle during an intermediate stage of the shot sleeve filling operation.

FIG. 6 is a cross sectional view of a bottom pour ladle during an end stage of the shot sleeve filling operation.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides, in some embodiments, a device to transfer liquidus alloy for making a squeeze cast product, a method of transferring liquidus alloy using the device, the cast product, and a system for making the cast product. Various embodiments of the invention are particularly suited for use in transferring liquidus magnesium and/or aluminum alloys.

Squeeze casting is a term of art used to describe a process of introducing liquid or semi solid alloy into a die and pressurizing the alloy in the die. The relative benefits of squeeze casting over traditional die casting methods include less to no turbulence, less to no air entrapment, reduced shrink porosity, and more rapid solidification. Squeeze casting also offers dimensional control that is comparable to that available with high pressure die casting (“HPDC”).

Squeeze casting is suitable for the production of a variety of components. In particular, thick-walled components or components having a thickness of about 2.5 mm or greater benefit from being produced in various squeeze casting devices. Additionally, there is less or no skin effect with squeeze casting as compared to traditional methods of casting, resulting in a component with higher integrity and less porosity. That is, squeeze casting imparts qualities to a metal that are difficult to achieve with conventional die casting, gravity permanent mold, or sand casting, including reduced or no porosity, higher mechanical integrity, improved wear resistance, and the ability to solution treat.

Examples of squeeze casting devices include: horizontal vertical squeeze casting (“HVSC”), vertical casting devices, and the like. HVSC devices are so named because the die clamp opens horizontally and the molten alloy is inserted vertically. In vertical casting devices, the die clamp opens vertically and, generally, the molten alloy is inserted vertically as well. In addition, a great variety of variations and conformation of squeeze casting devices exist. Some such variations are described herein, however, any suitable device for squeeze casting is within the purview of the present invention.

Components produced in a squeeze casting device are subjected to various optional post-casting procedures. These optional procedures include one or more of milling, finishing, chemical and thermal treatments, and the like. In a particular example, the component is subjected to a heat treatment, if desired, to enhance certain properties of the cast components, especially ductility. More particularly, mechanical properties of products generated by squeeze casting (squeeze casts) are generally enhanced by various heat treatments such as, for example, T6 tempering, T4 tempering, and the like.

FIG. 1 is a horizontal vertical squeeze casting (“HVSC”) system 10 for squeeze casting an alloy according to an embodiment of the invention. As shown in FIG. 1, the HVSC system 10 includes mold 12, shot sleeve 14, furnace or crucible 16, bottom pour ladle 18, and robotic system 20. In general, the HVSC system 10 may be utilized to cast an item 22 from a supply of liquidus alloy 24. For the purpose of this disclosure, the term, liquidus alloy refers to alloy held at a liquidus temperature. The liquidus temperature specifies the maximum temperature at which crystals can co-exist with the melt in thermodynamic equilibrium. Above the liquidus temperature the material is homogeneous. Below the liquidus temperature, crystals may begin to form in the melt, depending on the material.

The liquidus temperature can be contrasted with the solidus temperature. The solidus temperature quantifies the point at which a material completely solidifies (crystallizes). The liquidus and solidus temperatures may overlap. In this overlapping temperature range, a slurry or semi-solid metal may be formed. In this regard, squeeze casting may be performed with semi-solid metal.

The mold 12 includes a cavity corresponding to the item 22. In general, liquidus magnesium alloy may be introduced to the mold 12 in any suitable manner. In the particular embodiment shown in FIG. 1, the mold 12 includes an orifice configured to mate with the shot sleeve 14 to receive an injectant of liquidus alloy 24.

The shot sleeve 14 is configured to receive the injectant and introduce the injectant to the mold cavity. In various examples, the shot sleeve 14 may include a hydraulically driven piston 26 or other such actuator to urge the injectant into the mold cavity. As shown herein, the shot sleeve 14 may be moved out from under the mold 12 and/or tilted to receive the injectant from the bottom pour ladle 16.

The crucible 16 is configured to heat and/or retain the supply of liquidus alloy 24 at the liquidus temperature. Magnesium alloy is a particularly suitable alloy for use with HVSC system 10 and/or the crucible 16. The liquidus temperature of magnesium alloys varies widely depending upon the particular alloy composition. In a specific example, the liquidus temperature of the magnesium alloy AZ91D is about 1105° F. or 595° C. Typically, the alloy is heated somewhat beyond this temperature to allow for contact with relatively cooler surfaces without solidification of the alloy. Therefore, the casting temperature is about 1160° F. (625° C.) to about 1290° F. (700° C.).

In addition to AZ91D other magnesium alloys and or various aluminum alloys are suitable for use with the HVSC system 10. For example aluminum alloys A356, A380, A383, ADC-12 and the like are suitable for use with the HVSC system 10 and bottom pour ladle 18. Accordingly, the temperature of the crucible 16 and/or other components of the HVSC system 10 may vary depending upon the particular alloy utilized.

The bottom pour ladle 18 is configured to transfer the liquidus alloy 24 from the crucible 16 to the shot sleeve 14. The bottom pour ladle 18 includes a bowl 28, snout 30, aperture 32, stopper 34, and stopper shaft 36. The snout 30 either alone or together with the bowl 28 is configured to contain a sufficient volume of the liquidus alloy 24 to fill the shot sleeve 14. In this regard, all of the surfaces that come into contact with the liquidus alloy 24 are compatible with constituents of the liquidus alloy 24 and will not contaminate or otherwise react with the liquidus alloy 24. In a particular example, one or more of the bowl 28, snout 30, stopper 34, and stopper shaft 36 include surfaces of a stainless steel alloy Y06. Conventional ladles include ceramic components with a silica base. Silica reacts violently with liquidus magnesium and therefore silica can not be used to transfer liquidus magnesium.

In other embodiments, one or more of the bowl 28, snout 30, stopper 34, and stopper shaft 36 include surfaces of other ferrous materials or non-ferrous materials that are compatible with constituents of the liquidus alloy 24. As such, depending upon the particular liquidus alloy 24, the bowl 28, snout 30, stopper 34, and stopper shaft 36 may include surfaces of any suitable material.

To fill the snout 30 and/or bowl 28, the bottom pour ladle 18 may be positioned into the crucible 16 by the robotic system 20. For example, a controller 38 may control the robotic system 20 to place the bottom pour ladle 18 into the crucible 16. The stopper 34 is configured to mate with the aperture 32 and form a seal. The bottom pour ladle 18 includes an actuator 40 connected to the stopper shaft 38.

The actuator 40 may be controlled to urge the stopper towards the aperture 32 or away from the aperture 32. By urging the stopper 34 into contact with the aperture, the aperture 32 may be closed. To open the aperture 34 and allow the liquidus alloy 24 to enter the snout 30, the actuator 40 may be controlled, by the controller 36 for example, to urge the stopper 34 away from the aperture 32. The level to which the bottom pour ladle 18 is filled with the liquidus alloy 24 may depending upon the depth to which the bottom pour ladle 18 is placed in the crucible 16 and the level of the supply of liquidus alloy 24. In addition, by closing the aperture 34, the fill level of the bottom pour ladle 18 may be reduced. Conversely, by applying a vacuum to the bottom pour ladle 18, the fill level may be increased.

The robotic system 20 includes any suitable system of actuators that may be controlled to lift the bottom pour ladle 18, move the bottom pour ladle 18 between the crucible 16 and the shot sleeve 14, and as shown in FIG. 2, place the snout 30 into the shot sleeve 14. In this regard, the snout 30 is configured to fit within the shot sleeve 14. That is, the outside diameter of the snout 30 is less than the inside diameter of the shot sleeve 14. In addition, as shown in FIGS. 3-5, the robotic system 20 and/or a system to move the shot sleeve 14, may be configured to retract the snout 30 from the shot sleeve 14 substantially at the rate at which the shot sleeve 14 is filled.

FIG. 3 is a cross sectional view of the bottom pour ladle 18 at an initial stage of filling the shot sleeve 14 in accordance with an embodiment of the invention. As shown in FIG. 3, the aperture 32 is placed at a bottom portion of the shot sleeve 14. In general, the aperture 32 is as close to the bottom of the shot sleeve 14 as possible without impeding the flow of the liquidus alloy 24 therefrom. In a particular example, the aperture 32 is placed in close proximity to the piston 26. By placing the aperture 32 in close proximity to the bottom of the shot sleeve 14 prior to opening the aperture 32, the shot sleeve 14 may be filled with a minimum about of splashing and turbulence. This relatively calm flow of the liquidus alloy 24 from the aperture 32 greatly improves the overall casting quality of cast products. In particular the mechanical properties of the item 22 are improved by reducing the creation of oxides and other impurities.

According to various embodiments of the invention, the bottom pour ladle 18 may optionally include one or more heaters 42 and 44. If included, the heater 42 may be disposed upon or around the bowl 28 and configured to impart heat to the bowl 28 and any contents therein. If the heater 44 is included, it may be disposed in or around the stopper 34 and/or stopper shaft 36. The heater 44 is configured to impart heat into the contents of the bowl 28 and/or snout 30. The heaters 42 and 44 may include any suitable heating devices or elements. In a particular example, the heaters 42 and 44 may include a resistive metal element configured to generate heat in response to the application of current therethrough. In various embodiments, the heaters 42 and/or 44 may be controlled to provide sufficient heat energy to maintain the liquidus temperature of the liquidus alloy 24 or to raise the temperature of the liquidus alloy 24 in preparation to fill the relatively cooler shot sleeve 14.

In addition, according to an embodiment of the invention, the bottom pour ladle 18 may include an optional nozzle 46. If included, the nozzle 46 may be connected to an inert gas source via a hose or pipe 48. The nozzle 46 is configured to introduce a bath of inert gas into the bottom pour ladle 18. Depending upon the particular alloy utilized, the specific gas may be selected from suitable inert gasses. In a particular example, the inert gas may include Argon and/or SO₂. To retain the bath of inert gas and/or facilitate heat retention and/or reduce spillage, the bottom pour ladle 18 may include a lid 50. The lid 50 may be configured to cover a rim of the bowl 28 and form a seal thereon. In general, the lid 46 facilitates retention of the gasses within the bowl 28, however, the lid need not provide a gas impermeable seal.

FIG. 4 is a cross sectional view of the bottom pour ladle 18 at an intermediate stage of filling the shot sleeve 14 in accordance with an embodiment of the invention. As shown in FIG. 4, the aperture 32 is opened in response to the actuator 40 urging the stopper 34 via the stopper shaft 36 away from the aperture 32. In response to opening the aperture 32, liquidus alloy 24 is allowed to flow from the bottom pour ladle 18 into the shot sleeve 14. As shown in FIGS. 5 and 6, the bottom pour ladle 18 and shot sleeve 14 are drawn away from one another during the shot sleeve filling operation. In general, the bottom pour ladle 18 and shot sleeve 14 are drawn away from one another at approximately the rate at which the shot sleeve 14 fills with the liquidus alloy 24. In a particular example, the rate at which the bottom pour ladle 18 and shot sleeve 14 are drawn away from one another is controlled to retain the aperture just below the level of the rising the liquidus alloy 24 within the shot sleeve 14. The rate at which the shot sleeve 14 is filled—and thus the rate at which the snout 30 is drawn out of the shot sleeve 14—may be determined in any suitable manner. For example, the fill rate may be calculated, determined empirically and/or sensed via sensors in or around the shot sleeve 14.

As shown in FIG. 6, the aperture 32 may be closed in response to the completion of the shot sleeve filling operation. For example, the actuator 40 may be controlled to urge the stopper 34 via the stopper shaft 36 against the aperture 32. In this manner, any of the liquidus alloy 24 remaining in the bottom pour ladle 18 may be prevented from entering the shot sleeve 14 and/or spilling out as the bottom pour ladle 18 is returned to the crucible 16. In other examples, the bottom pour ladle 18 may be filled from the crucible 16 to contain the correct amount of the liquidus alloy 24 to fill the shot sleeve 14 and thus, the aperture closing procedure may be omitted.

The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. 

1. A bottom pour ladle device for transferring liquidus metal from a crucible to a shot sleeve, the device comprising: a bowl; a snout disposed below the bowl, the snout being configured to fit into the shot sleeve, wherein a distal end of the snout is configured to reach a bottom portion of the shot sleeve; an aperture at the distal end of the snout; a stopper to close the aperture in response to being urged against the aperture; an actuator to urge the stopper; and a stopper rod to connect the stopper to the actuator, wherein the bowl, snout, and aperture are comprised of materials compatible with liquidus alloy.
 2. The device according to claim 1, wherein the liquidus alloy is a liquidus magnesium alloy and wherein surfaces in contact with the liquidus magnesium alloy are compatible with the liquidus magnesium alloy.
 3. The device according to claim 2, wherein the surfaces in contact with the liquidus magnesium alloy are comprised of stainless steel alloy Y06.
 4. The device according to claim 1, further comprising: a lid to cover a top rim of the bowl.
 5. The device according to claim 1, further comprising: a heater to impart heat into the liquidus metal, wherein the heater is disposed at the stopper rod and the bowl.
 6. The device according to claim 1, further comprising: a connector to connect the device to a robotic system, the robotic system being configured to control the movement of the bottom pour ladle.
 7. The device according to claim 1, further comprising: an inert gas dispenser to dispense inert gas into the device.
 8. An apparatus for transferring liquidus alloy from a crucible to a shot sleeve, the apparatus comprising: means for disposing a bottom pour ladle in the crucible, the bottom pour ladle having a bowl and a snout disposed below the bowl, the snout having an aperture at a distal end; means for opening the aperture to allow an ingress of the liquidus alloy; means for closing the aperture to retain the liquidus alloy; means for disposing the distal end at a bottom portion of the shot sleeve; means for opening the aperture to allow the liquidus alloy to flow into the shot sleeve; and means for raising the bottom pour ladle, wherein the aperture is raised at a rate coinciding with a rate the shot sleeve fills with liquidus alloy and the aperture is controlled to remain relatively below a fill level of the shot sleeve.
 9. The apparatus according to claim 8, wherein the liquidus alloy is a liquidus magnesium alloy and surfaces of the apparatus in contact with the liquidus magnesium alloy are compatible with the liquidus magnesium alloy.
 10. The apparatus according to claim 9, wherein the surfaces of the apparatus in contact with the liquidus magnesium alloy are comprised of stainless steel alloy Y06.
 11. The apparatus according to claim 8, further comprising: means for heating a stopper rod to impart heat into the alloy, the stopper rod having a stopper end and an actuator end, the stopper end including a stopper being configured to mate with the aperture, the actuator end being affixed to an actuator.
 12. The apparatus according to claim 8, further comprising: means for urging the stopper towards the aperture to close the aperture.
 13. The apparatus according to claim 8, further comprising: means for heating the bowl to impart heat into the magnesium alloy.
 14. The apparatus according to claim 8, further comprising: means for dispensing an inert gas into the bowl.
 15. The apparatus according to claim 8, further comprising: means for opening a lid in conjunction with opening the aperture, wherein the lid is configured to cover a top rim of the bowl.
 16. The apparatus according to claim 15, further comprising: means for closing the lid in conjunction with closing the aperture.
 17. The apparatus according to claim 8, further comprising: means for connecting the bottom pour ladle to a robotic system, the robotic system being configured to control the movement of the bottom pour ladle.
 18. A method of transferring liquidus alloy from a crucible to a shot sleeve, the method comprising steps of: disposing a bottom pour ladle in the crucible, the bottom pour ladle having a bowl and a snout disposed below the bowl, the snout having an aperture at a distal end; opening the aperture to allow an ingress of liquidus alloy; closing the aperture to retain the liquidus alloy; disposing the distal end at a bottom portion of the shot sleeve; opening the aperture to allow the liquidus alloy to flow into the shot sleeve; and raising the bottom pour ladle, wherein the aperture is raised at a rate coinciding with a rate the shot sleeve fills with liquidus alloy and the aperture is controlled to remain relatively below a fill level of the shot sleeve.
 19. The method according to claim 18, wherein the liquidus alloy is a liquidus magnesium alloy and the bottom pour ladle includes surfaces in contact with the liquidus magnesium alloy that are compatible with the liquidus magnesium alloy.
 20. The method according to claim 19, wherein the surfaces of the bottom pour ladle in contact with the liquidus magnesium alloy are comprised of stainless steel alloy Y06.
 21. The method according to claim 18, further comprising: heating a stopper rod to impart heat into the magnesium alloy, the stopper rod having a stopper end and an actuator end, the stopper end including a stopper being configured to mate with the aperture, the actuator end being affixed to an actuator.
 22. The method according to claim 18, further comprising: urging the stopper towards the aperture to close the aperture.
 23. The method according to claim 18, further comprising: heating the bowl to impart heat into the magnesium alloy.
 24. The method according to claim 18, further comprising: dispensing an inert gas into the bowl.
 25. The method according to claim 18, further comprising: opening a lid in conjunction with opening the aperture, wherein the lid is configured to cover a top rim of the bowl.
 26. The method according to claim 25, further comprising: closing the lid in conjunction with closing the aperture.
 27. The method according to claim 18, further comprising: connecting the bottom pour ladle to a robotic system, the robotic system being configured to control the movement of the bottom pour ladle. 